The present invention relates to a pickup moving mechanism and a pickup moving method for an optical disk apparatus for introducing a laser beam into an optical disk to record or reproduce information. More particularly, the present invention relates to a pickup moving mechanism and a pickup moving method for an optical disk apparatus having a control function, or a so-called tilt servo mechanism, for maintaining perpendicularity between the optical disk and an optical axis of an optical pickup.
In an optical disk apparatus, it is essential that the angle between an optical disk (hereinafter, referred to as disk) and the optical axis of an optical pickup for introducing a laser beam to the disk and recording or reproducing information is an angle at which the optical disk is perpendicular to the optical axis. In an actual apparatus, however, the above-stated angle is deviated from the latter angle at which the optical disk is perpendicular to the optical axis because of warpage of the disk, tolerance accumulation of a mechanism section or the like, a mechanism for adjusting or controlling this angle is devised.
As an apparatus for adjusting the angle formed between the disk and the optical axis of the optical pickup, there is known an apparatus shown in Japanese Unexamined Patent Publication No. 10-116479. The constitution of the apparatus will be described based on FIG. 5.
A disk motor 2 rotating and supporting a disk (not shown) is fixed onto a base 1, and an optical pickup 3 introducing a laser beam to the disk and recording or reproducing information is supported by a pair of guide members 4 and 5 so that the optical pickup 3 is movable in the diameter direction of the disk. A pickup driving motor 6 for driving the optical pickup 3 is fixed to the base 1 and the motor 6 transmits a driving force to a screw member 7 supported by bearings 1a and 1b provided on the base 1 to be rotatable about a axial core through gears 8 and 9. An engagement member 10 having an inclined portion 10a engaged with the screw member 7 and converting the rotation of the screw member 7 into the movement of the optical pickup 3 is fixed to the optical pickup 3. One ends of the guide members 4 and 5 are supported by support portions 11 and 12 and tiltable about the support portions 11 and 12, respectively. The other ends of the guide members 4 and 5 are in contact with the tip ends of adjustment screws 14 and 15 which are engaged with the female threaded portions of a beam member 13 fixed to the base 1 and which move in the direction of the optical axis 3a of the optical pickup 3 by their own rotation while being pressed by urging means, respectively.
With the above-stated constitution, if the angle of the optical axis 3a of the optical pickup 3 with respect to the disk is deviated from the angle at which the optical axis 3a is perpendicular to the disk due to tolerance accumulation of the mechanism portion or the like, the deviation is detected by a signal from the optical pickup 3 or a tilt detection element, not shown. Due to this, by rotating the adjustment screws 14 and 15, the guide members 4 and 5 are tilted about the support portions 11 and 12, respectively, in the direction of the optical axis 3a, the optical pickup 3 supported by the guide members 4 and 5 is inclined with respect to the base 1 and the deviation of the optical axis 3a is adjusted. This angle adjusting device can be developed to an angle control device by driving the adjustment screws 14 and 15 using a motor.
As an optical disk apparatus utilizing angle control, there is known an apparatus shown in Japanese Unexamined Patent Publication No. 9-198687. The constitution of the apparatus will be described based on FIG. 6.
This optical disk apparatus is almost the same in constitution as that shown in FIG. 5. Namely, a disk motor 2 rotating and supporting a disk 16 is fixed on a base 1 and an optical pickup 3 introducing a laser beam to a disk 16 and recording or reproducing information is supported by a pair of guide members 4 and 5 so that the optical pickup 3 is movable in the diameter direction of the disk 16.
It is noted, however, a tilt detection element 17 for detecting the angle between the disk 16 and the optical axis 3a of the optical pickup 3 is provided on the optical pickup 3. Also,a pickup driving motor 6 for driving the optical pickup 3 is fixed to the base 1, and driving gears 18 and 19 engaged with the driving shaft of this pickup driving motor 6 are rotatably supported. An engagement member 10 which is engaged with this driving gear 19 and to which the driving force of the pickup driving motor 6 is transmitted through the driving gears 18 and 19 is provided to be fixed to the optical disk 3.
One ends of the guide members 4 and 5 are supported by support portions 11 and 12, respectively, while the other ends of the guide members 4 and 5 are supported by an elevation member 20 provided to be movable in a direction perpendicular to the base 1. The guide members 4 and 5 are tiltable about the support portions 11 and 12, respectively by the elevation member 20. The perpendicular movement of the elevation member 20 is based on the engagement of cam followers 20a formed on the both sides of the elevation member 20 with eccentric cams 22 fixed to the output shaft of tilt motors 21 fixed to the base 1, respectively.
With the above-stated constitution, if the angle of the optical axis 3a of the optical pickup 3 with respect to the disk 16 is deviated from an angle at which the optical axis 3a is perpendicular to the disk 16, the deviation is detected by a tilt detection element 17. Based on the detected deviation, the tilt motors 21 rotate, the elevation member 20 engaged with these tilt motors 21 through the eccentric cams 22 and the cam followers 20a move in the perpendicular direction, respectively, whereby the guide members 4 and 5 tilt about the support portions 11 and 12 in the direction of the axis 3a, respectively. As a result, the optical pickup 3 supported by the guide members 4 and 5 are inclined with respect to the base 1 and the deviation of the optical axis 3a is adjusted.
However, if the angle adjusting device shown in Japanese Unexamined Patent Publication No. 10-116479 is developed to an angle control device for driving adjustment screws by a motor, the following problems occur. If the optical pickup 3 is moved in the disk diameter direction, it is necessary to exercise movement control while detecting the position of the optical pickup 3. To do so, detection means such as a photo-interrupter is normally attached to either the pickup driving motor 6 or the screw member 7, or the pickup driving motor 6 is used as a stepper motor and the position of the optical pickup 3 is detected using the driving pulse of the motor 6, and the optical pickup 3 is moved to a predetermined position based on a detection result. In that case, the optical axis 3a of the optical pickup 3 thus moved does not sometimes agree with a target position on the disk to and from which information is to be recorded or reproduced. If the axis 3a does not agree with the target position, the optical characteristics of the optical pickup 3 may possibly deteriorate or the optical pickup 3 may be possibly required to be moved again, thereby disadvantageously increasing access time. The problems stated above will be described with reference to FIG. 7.
FIG. 7 is a view showing the essential parts of the device described with reference to FIG. 5 seen from a different observation point. FIG. 7(a) is a top view seen from the direction of the optical axis 3a of the optical pickup 3 and FIG. 7(b) is a side view of FIG. 7(a) except for the screw member 7. In FIG. 7(b), reference symbol 10a denotes an inclined portion formed on the engagement member 10 and the engagement member 10 is engaged with the screw member 7 on this inclined portion 10a. Since the screw member 7 is a right-hand screw, the inclined portion 10a is inclined by predetermined angle in a clockwise direction with reference to the optical axis 3a. 
The engagement portion between the screw member 7 and the engagement member. 10 is typically shown in FIG. 7(c). In FIG. 7(c), the disk 16 is arranged in parallel to the base 1. The axial core 4a of the guide member 4 is, therefore, arranged in a direction along the base 1 and the optical pickup 3 moves to a position away from the support portion 11 by a distance r1. Namely, in response to an instruction to move the optical pickup 3 to the position away from the support portion 11 by the distance r1, the screw member 7 moves the inclined portion 10a engaged with the inclined surface 7a of the screw member 7 to the position shown in FIG. 7(c) in the direction along the base 1. The optical axis 3a of the optical pickup 3 to which the inclined portion 10a is fixed, extends perpendicularly to the base 1 and a position on the disk indicated by the intersection between the optical axis 3a and the disk 16 (hereinafter, referred to as disk diameter position) is located at a position away from the support portion 11 by a distance r2 (=r1).
FIG. 7(d) shows a case where the disk 16 is inclined. In FIG. 7(d), the disk 16 is inclined in a counterclockwise direction and the axial core 4a of the guide member 4 tilts downward toward the position shown in FIG. 7(d) around the support portion 11 according to the inclination of the disk 16. At this moment, a position detection signal obtained from the screw member 7 or the pickup driving motor is the same as that in the case of FIG. 7(c) described above. The inclined surface 7a of the screw member 7, therefore, moves to a position away from the support portion 11 by the distance r1 as in the case of FIG. 7(c). On the other hand, the inclined portion 10a engaged with the inclined surface 7a of the screw member 7 is slid downward and arranged at a position away from the support portion 11 by a distance r3 since the axial core 4a of the guide member 4 is shifted downward by tilting. As a result, a difference is generated between the position away from the support portion 11 by the distance r3 and the position away from the support portion 11 by the distance r1 on which the inclined portion 10a and the optical axis 3a are to be arranged. In addition, since the optical axis 3a of the optical pickup 3 to which the inclined portion 10a is fixed is in the direction perpendicular to the axial core 4a of the guide member 4, an actual disk diameter position indicated by the intersection between the optical axis 3a and the disk 16 is located at a position away from the support portion 11 by a distance r4. As a result, the distance between the position away from the support portion 11 by the distance r4 and the distance away from the support portion 11 by the distance r1 further increases.
As measures taken against the disagreement between the disk diameter position on which the optical axis 3a is to be arranged and the actual disk diameter position as stated above, it is contrived to drive the optical pickup 3 not by the screw member but by gears as in the case of the apparatus shown in Japanese Unexamined Patent Publication No. 9-198687 stated above. This driving method can be assumed as a case where a surface denoted as the inclined surface 7a in FIGS. 7(c) and 7(d) is parallel to the optical axis 3a. According to this driving method, however, while the diameter position r3 shown in FIG. 7(d) agrees with the diameter position r1, the diameter position r4 still differs from the diameter position r3. Furthermore, compared with the driving method using the screw member, this driving method has disadvantages of an increase in the number of parts, the deterioration of the positional accuracy of the optical pickup 3 due to backlash which occurs between the driving gears 18 and 19 shown in FIG. 6, the occurrence of hysteresis and the like. Besides, since inertia is normally high, this driving method has a disadvantage in that response frequency is low.
The present invention has been made to solve the above-stated problems and an object of the present invention is to provide a pickup moving mechanism for an optical disk apparatus using screw members as pickup driving means, capable of making it difficult to generate a positional deviation between the optical axis of an optical pickup and a target position on a disk even if the optical pickup is inclined so as to maintain perpendicularity between the disk and the optical pickup.
To obtain the above-stated object, the invention recited in claim 1 is an optical disk apparatus pickup moving mechanism comprising: a guide member supporting an optical pickup introducing a laser beam to an optical disk and recording or reproducing information, and guiding the optical pickup to move in a disk diameter direction; pickup driving means for driving the movement of the optical pickup; position detection means for detecting a position of the optical pickup in the disk diameter direction; tilt detection means for detecting an angle deviation of an optical axis of the optical pickup moved by a preset distance with respect to a recording or reproducing target position on the optical disk in the disk diameter direction; and tilt driving means for tilting the guide member in accordance with an output of the tilt detection means, and for inclining the optical pickup supported by the guide member in a direction in which the angle deviation of the optical axis decreases, characterized by providing control means for controlling the pickup driving means so as to move the optical pickup in a direction in which the deviation of the optical axis in the disk diameter direction generated by inclination of the optical pickup decreases.
According to the above-stated constitution, while inclining the optical pickup by the tilt driving means so as to control the angle between the optical disk and the optical axis of the optical pickup, the deviation of the optical axis of the optical pickup in the disk diameter direction generated by the inclination can be decreased by moving the optical pickup by the pickup driving means. It is, therefore, possible to introduce a laser beam to a target position on the optical disk to or from which position information is recorded or reproduced.
The invention recited in claim 2 based on the constitution of claim 2 is characterized by constituting the pickup driving means to comprise: a screw member provided along the guide member and rotating about an axial core; an engagement member provided at the optical pickup, engaged with the screw member, and converting rotation of the screw member into movement of the optical pickup in the disk diameter direction; and a rotation driving portion driving the rotation of the screw member.
The invention recited in claim 3 based on the constitution of claim 1 is characterized by constituting the tilt driving means to comprise: a support portion tiltably supporting the guide member in a direction in which the guide member approaches and separates from a base; urging means, provided between one end portion of the tiltable guide member and the base, for urging the one end portion of the guide member in a direction in which the one end portion separates from the base; pressing means provided to face the one end portion of the guide member to be able to be freely elevated, and capable of pressing the one end portion of the guide member against an urging force of the urging means; and elevation driving means for driving elevation of the pressing means in accordance with an output of the tilt detection means.
The invention recited in claim 4 based on the constitution of claim 2 is characterized by providing an inclined portion of the engagement member engaged with a threaded groove of the screw member is provided so that an angle of the inclined portion with the optical axis of the optical pickup is greater than 0 and a tangent thereof is smaller than 2L/R while information is recordable or reproducible up to a position of a diameter R on the optical disk and a distance between a support portion supporting the other end portion of the guide member and the optical disk is L.
By setting the angle of the inclined portion to fall within the above-stated range, it is possible to make the deviation of the optical axis of the optical pickup in the disk diameter direction derived from the inclination of the optical pickup smaller. The threaded groove of the screw member with which the inclined portion can be engaged is provided.
The invention recited in claim 5 is characterized in that: when an optical pickup introducing a laser beam to an optical disk and recording or reproducing information is supported by a guide member and moved in an optical disk diameter direction, the optical pickup is moved along the guide member by a preset distance with respect to a recording or reproducing target position on the optical disk while detecting a position of the optical pickup in the disk diameter direction; an angle deviation of the moved optical pickup from an optical axis in the disk diameter direction is detected; the guide member is tilted based on a detection result, and the optical pickup supported by the guide member is inclined in a direction in which the angle deviation of the optical axis decreases; and the optical pickup is moved in a direction in which the deviation of the optical axis in the disk diameter direction decreases by inclination of the optical pickup.
According to the above-stated constitution, while inclining the optical pickup so as to control the angle between the optical disk and the optical axis of the optical pickup, the deviation of the optical axis of the optical pickup in the disk diameter direction generated by the inclination is decreased by moving the optical pickup. It is, therefore, possible to introduce a laser beam to a target position on the optical disk to and from which position information is recorded or reproduced.
The invention recited in claim 6 based on the constitution recited in claim 5, is characterized in that when the optical pickup is inclined in a direction in which the optical pickup approaches the optical disk, the optical pickup is moved toward an outer peripheral side of the optical disk in the disk diameter direction.
According to the optical disk apparatus pickup moving mechanism of the present invention, the tilt driving means for inclining the optical pickup so that the optical disk is perpendicular to the optical axis of the optical pickup, and control means for controlling the pickup driving means so as to move the optical pickup in the direction in which the deviation of the optical axis generated by the inclination of the optical pickup decreases are provided, whereby a laser beam can be introduced to the target position of the optical disk to or from which information is recorded or reproduced by decreasing the deviation.
As the pickup driving means, a screw member is provided along the guide member, an engagement member engaged with the screw member is provided at the optical pickup and a rotation driving portion driving the rotation of the screw member is provided, for example, whereby the rotation of the screw member can be converted into the movement of the optical pickup in the disk diameter direction. At this time, when information up to a diameter R position on the optical disk can be recorded or reproduced and the distance between the support portion supporting the other end of the guide member and the optical disk is L, the deviation of the optical axis of the optical pickup in the diameter direction can be made smaller by providing the inclined portion of the engagement member engaged with the threaded groove of the screw member so that the angle between the optical disk and the optical axis of the optical pickup is greater than 0 and that a tangent thereof is smaller than 2L/R.
Furthermore, according to the pickup moving method for an optical disk apparatus of the present invention, the optical pickup supported by the guide member is moved in the disk diameter direction, the angle deviation of the optical axis in the disk diameter direction is detected, the guide member is tilted based on the detection result and the optical pickup is inclined in the direction in which the angle deviation of the optical axis decreases, and the optical pickup is moved in the direction in which the deviation of the optical axis in the disk diameter direction generated by the inclination decreases, whereby a laser beam can be introduced to the target position on the optical disk to and from which information is recorded or reproduced while decreasing the deviation.